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Morales-Betancourt, Mónica A.; Lasso, Carlos A.; Bello, Laura C.; de Paula Gutiérrez, Francisco Potential distribution of the ( intermedius Graves 1819) in the of Colombia and Biota Colombiana, vol. 15, núm. 1, 2014, pp. 124-136 Instituto de Investigación de Recursos Biológicos "Alexander von Humboldt" Bogotá, Colombia

Available in: http://www.redalyc.org/articulo.oa?id=49140739009

How to cite Complete issue Scientific Information System More information about this article Network of Scientific Journals from Latin America, the Caribbean, Spain and Portugal Journal's homepage in redalyc.org Non-profit academic project, developed under the open access initiative Potential distribution of the (Crocodylus intermedius Graves 1819) in the Orinoco basin of Colombia and Venezuela Distribución potencial del caimán del Orinoco (Crocodylus intermedius Graves 1819) en la Orinoquia colombiana y venezolana

Mónica A. Morales-Betancourt, Carlos A. Lasso, Laura C. Bello & Francisco de Paula Gu- tiérrez

Abstract Crocodylus intermedius (Graves 1819), commonly known at the Orinoco Crocodile, is an endemic species of the Orinoco Basin that occurs in Colombia and Venezuela. Within the Neotropical Crocodylia, it is considered the most endangered species, listed as Critically Endangered. The use of potential distribution models is an important tool in biogeographical analysis for the conservation of rare and endangered species threatened with . For this reason in this study we determined the potential distribution range for the Orinoco Crocodile using the maximum entropy model Maxent. Initial data to calculate potential range included 654 records of known occurrence for this species, 20 environmental and one limnological variable. The distribution of the Orinoco Crocodile was found to be correlated with precipitation climate variables and the type of water (white, clear or black).

Key words. Orinoco River Basin. Crocodylus intermedius. Water type. Endangered species. Conservation.

Resumen Crocodylus intermedius (Graves 1819) comúnmente denominado caimán llanero o caimán del Orinoco, es una especie endémica de la cuenca del Orinoco, con distribución en Colombia y Venezuela. Dentro de los Crocodylia del Neotrópico, es considerada la especie más amenazada y se encuentra en la categoría de Peligro Crítico. El uso de modelos de distribución potencial en el análisis biogeográfico es una herramienta importante para la conservación de especies raras o en peligro de extinción. Es por ello que en este trabajo se buscó determinar la distribución potencial del caimán llanero mediante el uso del algoritmo de maximización de la entropía, Maxent. Como información de entrada se utilizaron 654 registros de presencia de la especie y 20 variables ambientales incluyendo una limnológica. Se concluye que la distribución del caimán llanero está relacionada con la precipitación y con el tipo de aguas (blancas, claras y negras) presentes en la cuenca.

Palabras clave. Cuenca del río Orinoco. Crocodylus intermedius. Tipos de aguas. Especie amenazada. Conservación.

124 Biota Colombiana 15 - Suplemento 1 - 2014 Biota Colombiana 15 - Suplemento 1 - 2014 125 Morales-Betancourt et al. Potential distribution of the Orinoco crocodile (Crocodylus intermedius Graves 1819) in the Orinoco basin of Colombia and Venezuela

Introduction Crocodylus intermedius (Graves 1819) is a critically in Venezuela (GECV) published an Action Plan: endangered species endemic to the Orinoco River Survival of the Orinoco Crocodile in Venezuela 1994 Basin in Colombia and Venezuela (http://www. -1999 (FUDENA 1993), and in 1994 the Ministerio iucnredlist.org/). Its critical status is due principally del Ambiente published a Strategic Plan: Survival of to extreme overharvest of their populations during the the Orinoco Crocodile in Venezuela (Profauna 1994). first half of the twentieth century (Medem 1981). More recently in 2007 the National Strategy for the Conservation of the Orinoco Crocodile in Venezuela In the two countries where C. intermedius occurs, and Action Plan was updated and published (GECV different conservation actions have been taken. 2007). Hunting and collection were prohibited in Colombia by Resolution Nº 411 enacted by the Breaking a world record for reintroductions of this Ministry of Agriculture in 1968. In 1997 the species kind, from 1990 to 2010 more than 7600 Orinoco was declared to be critically endangered in Resolution were released into the wild in Venezuela 676 and in 1998 the Ministerio del Medio Ambiente, (Seijas 2011). Studies in situ have shown that a the Instituto de Investigación de Recursos Biológicos new population with at least 400 subadult and adult Alexander von Humboldt (IAvH) and the Universidad individuals has been established in the Caño Guaritico Nacional de Colombia-Unal, formulated the National Refuge, in the section that is part of Hato El Frío in Conservation Plan for the Orinoco Crocodile the state of , which throughout the world is (Procaimán). Their principal objective was to “prevent considered to be a remarkable success, especially the extinction of the species and promote its recovery, considering that for the first time a stable crocodile to thus contribute to their conservation and integration population has become established based exclusively into regional economic and cultural systems” (MMA on specimens raised in captivity (Antelo 2008). et al. 1998). Within the framework of that plan various projects and activities have been carried out, mainly These in situ conservation projects of the Orinoco by the Tropical Biological Station “Roberto Franco”. Crocodile in Venezuela have generated fruitful local These initiatives have been focused on ex situ results, and so could serve as examples to be replicated conservation, so today development of in situ projects in habitats where crocodiles might be reintroduced, or are a top priority in Colombia. where extant populations need reinforcement. To be able to do that successfully it is essential to know the Meanwhile in Venezuela, the first legal actions to potential distribution of the species, which because it conserve C. intermedius - given the evidence that continues to be critically endangered, is today absent indicated extremely reduced population numbers from much of its original natural range. It should be - were taken in the 70’s of the last century. First, possible to return the Orinoco Crocodile to regions hunting was prohibited (as it was for many other where it is currently locally extinct, recovering at species) by a decree issued on April 4, 1973, a least part of its previous natural distribution and decision later ratified by presidential resolution in contributing to the reestablishment of populations that 1979 (Seijas 2011). Diverse conservation strategies could restore equilibrium in aquatic ecosystems where were then implemented, including a captive breeding it has been extirpated. program that started in the mid 80’s. In addition, the Caño Guaritico Wildlife Refuge, Fishing Reserve and For this purpose, species distribution modelling tools Protection Zone was created by decree Nº 2702 of (MDE) are especially useful. These tools are based, 1989. This protected area was used as a pilot project either explicitly or implicitly, on the ecological for the reintroduction into natural systems of Orinoco niche concept of Hutchinson (1957) and take into crocodiles raised in captivity. Since 1990, the release account climate and geomorphologic parameters of captive-raised has become routine in that determine the niche of each species (Martínez- several sites of the Venezuelan (Seijas 2011). Meyer 2005). The delimitation of the niche for each Furthermore, in 1993 the Crocodile Specialist Group species is created using geographic overlays that plot

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the records of species occurrence in multidimensional In this report our objective is to generate information environmental space using climate and geographic about the potential distribution of the Orinoco layers available in geographic information systems Crocodile that will be useful to the efforts for its (GIS). Starting there, the different MDE methods use conservation, especially with regard to possible areas different rules and mathematical algorithms to define where reintroduction could be successful, or where niche boundaries for each species. Once an abstract reduced populations need reinforcement. niche definition is obtained, dots from occurrence records are projected into geographic space to produce a predictive map of potential distribution (Tsoar et al. Materials y methods 2007). Study area These models have been widely used to determine The Orinoco River Basin is a binational drainage shared places of particular interest for conservation, sites between Venezuela (65 %) and Colombia (35 %), with where species can be reintroduced (Martínez-Meyer a total surface area of 991,587 km2, of which 347,165 et al. 2006), sites where future exploration is required km2 are in Colombian territory (Domínguez 1998) (Pearson et al. 2007) and are currently being used (Figure 1). In water volume the Orinoco is the third to predict changes in species distributions caused by largest river in the world. Along its 2,150 km length, climate change (Martínez-Meyer 2005, Phillips et al. tributaries drain the Shield, the Eastern 2006). slopes of the northern Mountains, the Coastal

Figure 1. Orinoco River Basin.

126 Biota Colombiana 15 - Suplemento 1 - 2014 Biota Colombiana 15 - Suplemento 1 - 2014 127 Morales-Betancourt et al. Potential distribution of the Orinoco crocodile (Crocodylus intermedius Graves 1819) in the Orinoco basin of Colombia and Venezuela

Mountain Range of Venezuela, plains of the Amazon regions: the Guyanese Orinoco, Orinoco Andes, Basin transition region, and the seasonally flooding coastal Orinoco, the Orinoco plains, the Orinoco high plains and high plains (llanos) of western Colombia plains, the Orinoco-Amazon transition zone and the and the eastern-central region of Venezuela to finally flooded riparian corridors of the main channel and its form a delta at its juncture with the tributaries: Upper Orinoco, and lower . (Rosales et al. 2010). Model of potential distribution The Orinoco River Basin includes with the To model potential distribution of the Orinoco three main types of water as defined by Sioli (1975) Crocodile (Crocodylus intermedius) the MaxEnt that mainly differ in their apparent color: white algorithm was considered to be more efficient than (turbid), clear (more or less transparent) and black other predictive models (Elith et al. 2006, 2011). (tea-colored). Whitewater rivers are more productive MaxEnt is based on the principle of maximized and richer in nutrients and electrolytes, have high entropy (version 3.3.3.k) (Phillips et al. 2006, conductivity, pH near neutral (6.2-7.2), and owe their Phillips and Dudík 2008), that seeks to generate color to the turbidity caused by suspended inorganic distributions of probability that involve the greatest sediments, such as illite and motmorillonite clays level of uncertainty in situations with incomplete data that are transported from the Andes Mountains to the (Raynal 2008), that is to say, it only uses presence alluvial plains (Lasso 2004). data (occurrence sites). The result from MaxEnt is a geographic potential distribution model for the Blackwater rivers originate in the Orinoco Guiana species inferred from climate parameters (Elith et Shield or the peneplains of Precambrian origin, and al. 2006). The model correlates presence data for the drain sandy soils of floodplain forests, acquiring species with environmental parameters. Each site of their characteristic tea color from the great quantity occurrence is taken to be a source location instead of decomposing organic material that leach from of a sink location, assuming that the conditions podsoils or histosoils. Their transparent but darkly where the species is present are optimal to define its stained water is low in conductivity, with acid pH due fundamental niche (Phillips et al. 2006). Based on to the large number of soluble acids (especially fulvic these correlations MaxEnt determines the ecological and humic) that leach from organic material (Sioli niche of each species and assigns a probability of 1975, Lasso 2004). Because of these characteristics occurrence to each pixel (cell) in the predetermined they are less productive (oligotrophic) than white or space (Phillips et al. 2006). clearwater rivers. The variables that were used to apply the model Most rivers with clear water originate on flat terrain, were: records for the occurence of the species, covered with forests that attenuate the erosive effects climate information, limnological or hydrochemical of the rains that penetrate the soil without producing information (water type: white, clear, or black). runoff (Sioli 1975). These waters are transparent The algorithm was given occurrence records from or greenish, depending on the hydrochemistry both countries based on collection or observation of characteristics of the soil through which they flow. the species from different sources such as scientific They tend to become turbid in the rainy season, have publications (Godshalk 1978, Medem 1981, varying pH (from 4.5-7.8) less acid than blackwaters Thorbjarnarson y Hernández 1992, Castro et al. but more acid than clearwater streams (Lasso 2004). 2012, Clavijo & Anzola 2013), grey literature (Lugo They are typically found on the and & Ardila-Robayo 1998), databases and personal high plains (Rosales et al. 2010). In figure 2 rivers of observations of researchers. If occurrence records are each water type are shown. geographically skewed (for example by oversampling in some regions) valid predictive models can be In an ecosystemic framework including both terrestrial applied, if and when the geographic array of records is and aquatic ecoregions (taking into account shoreline representative of the environmental habitat variability corridors), Rosales et al. (2010), recognized ten major present in the study area (García et al. 2011).

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a b

c d

Figure 2. Types of water in the Colombian Orinoco River Basin: a) (whitewater), b) caño Dagua (clearwater), c) (blackwater), d) of Inírida river (black) with Guaviare river (whitewater).

Nineteen Worldclim bioclimatic variables and one Two models were tested, one with occurrence data hydrological variable were used (Table 1) for the and climate (model 1) and the other adding the water selected area, with a resolution of 30 seconds (1 km type variable (model 2), to see which gave a better fit, aprox.) (Hijmans et al. 2005). The climate layers taking into consideration that the Orinoco Crocodile is available in Worldclim were interpolated using a world an aquatic species. meteorological network that incorporates averages mainly from the period from 1960-1990 (Hijmans et In each model the records were divided into 75 % al. 2005). for training and 25 % for evaluation. The models were evaluated using the statistical procedure “area With respect to the limnological information, a below the curve” (AUC) by cross validation. This map of water types using the Sioli (1975) system procedure assumes values from 0 to 1 and measures was constructed: white, clear and black. This was the discriminatory capacity of the models. A value done using the Arcgis 10.1 program. Information of 1 corresponds to perfect discrimination between was compiled from various sources: bibliographic areas of presence and absence; a value of 0.5 indicates information (Vegas-Villarrubia et al. 1988a, b, Lasso discrimination not significantly different from that 2004, Galvis et al. 2007), limnological databases from expect by chance. Models with scores above 0.7 are NGOs, and consultation with experts. considered acceptable (Fielding & Bell 1997).

128 Biota Colombiana 15 - Suplemento 1 - 2014 Biota Colombiana 15 - Suplemento 1 - 2014 129 BC-164 Potential distribution of the Orinoco crocodile (Crocodylus intermedius Graves 1819) in the Orinoco basin of Colombia and Venezuela FINAL AJUSTADO

Morales-Betancourt et al. Potential distribution of the Orinoco crocodile (Crocodylus intermedius Graves 1819) in the Orinoco basin of Colombia and Venezuela

Table 1. Bioclimatic variables. Table 1. Bioclimatic variables. Variable Significance BIO 1 Mean annual temperature BIO 2 Mean diurnal temperature range [(T0 máx-T0 min) monthly mean)]. BIO 3 Isothermality [(Bio2/Bio7) x 100] BIO 4 Temperature seasonality (standard deviation x 100) BIO 5 Maximum temperature in hottest month BIO 6 Minimum temperature in coolest month BIO 7 Annual temperature range (Bio5-Bio6) BIO 8 Mean temperature in trimester with highest rainfall BIO 9 Mean temperature in driest trimester BIO 10 Mean temperature of hottest trimester BIO 11 Mean temperature of coolest trimester BIO 12 Annual precipitation BIO 13 Precipitation of wettest month BIO 14 Precipitation BIO 15 Precipitation seasonality (coefficient of variance) BIO 16 Precipitation of wettest trimester BIO 17 Precipitation of driest trimester BIO 18 Precipitation of hottest trimester BIO 19 Precipitation of coolest trimester

Results To use the models, 654 occurrence records from both In the drainage (and its subdrainge, the countries were used l (Figure 3) and a water type River), specifically in the River map was constructed for the Orinoco River Basin systems, the area of highest probability of favorable (Figure 4). habitat conditions for the species is found, followed by the drainage. On the Colombian side, Application of model 1 included the 19 climate there are high probabilities of favorable habitat in parameters and occurrence of C. intermedius. The the drainage, especially in the Lipa-Ele- graphic output from the MaXent is shown in figure Cravo Norte systems and its mouth with the Casanare 5. The model had an AUC value of 0.86. According River, as well as the lower portion of the Meta River to the potential distribution model, it can be observed drainage. To a lesser degree, the upper Vichada and that the north-western region of the basin has a high Guaviare River were classified as favorable, especially probability of favorable conditions for the Orinoco the Duda-Guayabero system. Crocodile, and that the probability diminishes to the southeast. In the eastern part of the basin, the In table 2 the percent contribution of the most probability of favorable conditions is very low. significant (> 10 %) parameters are shown for both models. Variables Bio14 (precipitation in driest month) The result from model 2 had a higher AUC value of and Bio15 (precipitation seasonality), contributed 0.93. The graphic output (Figure 6) shows that in the most to model 1, but in model 2 water type (distance Venezuelan Orinoco Basin only in the northwest section to blackwater rivers and distance to whitewater rivers, are favorable conditions indicated for this species. and temperature seasonality contributed more.

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Figure 3. Records of occurrence of Crocodylus intermedius.

Figure 4. Water type map for the Orinoco River Basin.

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Figure 5. Model 1 of potential distribution of Crocodylus intermedius. In the image, colors indicate the probability of favorable conditions. Red indicates high probability of adequate conditions for the Orinoco Crocodile, yellow indicates conditions similar to those where this species is currently found, and shades of blue indicate low and lowest probabilities of adequate habitat conditions for this species.

Figure 6. Model of potential distribution for Crocodylus intermedius. In the image, colors indicate the probability of favorable conditions. Red indicates high probability of adequate conditions for the Orinoco Crocodile, yellow indicates conditions similar to those where this species is currently found, and shades of blue indicate low and lowest probabilities of adequate habitat conditions for this species.

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Table 2. Percent contribution of each variable to model results (model 1: AUC = 0.86; model 2: AUC = 0.93). Table 2. Percent contribution of each variable to model or seasonably flooding savannahs (Rosales et al. results (model 1: AUC = 0.86; model 2: AUC = 0.93). 2010). This region is drained by rivers flowing from the Andean piedmont (around 200 m a.s.l.), through Variable Model 1 Model 2 high and low llanos to join with the mainstem of Black waters 18.5 the Orinoco River at elevations less than 100masl White waters 18.4 (Rosales et al. op. cit.), the Orinoco Crocodyle is Bio 4 16.6 found up to 300 m a.s.l. (Godshalk 1978). These rivers begin in the Andes as clear water streams that Bio 14 15.2 gather ever more sediments from lateral terrestrial Bio 15 14.7 erosion as they descend eventually becoming turbid Clear waters 12.2 whitewater rivers carrying heavy loads of sediment Bio 3 11.3 and nutrients (Rosales et al. 2010). In the map in figure 6 for example, the intensity of color increases towards the lower parts of the rivers tributary to the Discussion Meta River (Guapanapalo, Pauto, and Guachiría rivers). Thus, in the lowest portion of the Meta River Both models indicate a high probability of favorable Basin we observe a high probability of favorable habitat conditions for the Orinoco Crocodile in the crocodile habitat. This pattern of increasing turbidity north-western part of the Orinoco River Basin (the due to sediments is associated with both suspended Cojedes, Apure, Portuguesa, Arauca and Meta River and dissolved solids, and is directly related to the drainages), with diminishing probability towards the productivity of these waters (Lasso 2004). south. In the eastern portion of the Orinoco River Basin there is a very low probability of favorable The (Venezuela) where the highest habitat. The area indicated as having favorable habitat probability of favorable habitat conditions was conditions correlates with areas known to have observed is home to the most robust C. intermedius abundant Orinoco Crocodile populations in the past population known to still exist at this time (Medem according to accounts of naturalists like Alexander 1983, Espinosa-Blanco & Seijas 2012). It is a von Humboldt (1875) and Federico Medem (1981, whitewater river, with a pH near neutral (pH 7 - 8) 1983). Those authors mention that the rivers with (Seijas 1998), characteristic of rivers of its type, such the highest numbers of crocodiles were the Arauca, as the Arauca (pH 6.7 Yánez & Ramírez 1988) and the Meta, Guayabero and Vichada in Colombia and the Meta (pH 7-8). Apure, Portuguesa, Arauca and mainstem Orinoco in Venezuela. In the Orinoco llanos some rivers originate in the plains, such as the eolic plains of the Capanaparo and Model 1 is a conventional model since it employs Cinaruco rivers (Iriondo 1997). These rivers have clear commonly selected variables (records of occurrence water that darkens during the dry season to a dark tea and climate data) for this type of analysis. The color as observed in rivers classified as blackwater. inclusion of water type (white, clear, or black) in For this area we can see how water type influences model 2 gave a better fit of potential habitat with areas model predictions. Model 1 predicts medium habitat known to have abundant crocodile populations in the suitability for the upper stretches of these two rivers past. The distribution of aquatic organisms is highly but with model 2, where water type is included, the correlated to the productivity of the waters, and so predicted suitability drops considerably. In any case, perhaps reflects the availability of potential prey to a there is a viable population of Orinoco Crocodiles carnivorous species like C. intermedius. living today in the lower stretch of the Capanaparo River (Medem 1983, Llobet & Seijas 2003, Espinosa- In general terms, the highest probability of favorable Blanco & Seijas 2012). habitat conditions corresponds to the Orinoco llanos,

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The hydrochemistry (water type) and hence the In addition, in the north-western part of the basin productivity of the system is determinant for the of the Cojedes River drainage where the models distribution, abundance and biomass of the aquatic predict the highest habitat favorability, rainfall is biota, especially which are the principal food low (Rosales et al. 2010). In model 1 the variables source for Orinoco Crocodiles. It is for this reason that that most contribute to predictions are precipitation water type affects the distribution of C. intermedius in the driest month (Bio14) and seasonality of and other crocodilians in the Orinoco River Basin. precipitation (Bio15). According to Gorzula et al. However, other parameters are also related such as (1988), this species’ populations are associated with soil type and climate, among others. For example, low precipitation (644 ± 1.797 mm). The distribution in the whitewater Guaviare River (Colombia) of rainfall throughout the year also influences the one might reasonably expect high probability of distribution of this species. In the south-eastern favorable habitat conditions, but the model predicts portion of the basin, where northeast trade wins bring the opposite. This is possible due to the presence the highest amount of annual rainfall (2.500 to 3.500 of relictual formations of the Guyana Shield in this mm) (Rosales et al. 2010) we find the least probability region similar to those found in the eastern part of of favorable crocodile habitat. the where low probabilities of suitable habitat are also predicted by the model. Although the Guaviare River is whitewater, it has Conclusions lower conductivity (30 µS) (Ideam 1995), and is not According to the model of potential distribution, the as productive as other whitewater rivers such as the geographic distribution area of C. intermedius is to a Arauca (120 µS, Yánez & Ramírez 1988). Along large degree influenced by physical factors such as the length of the Guaviare River’s flow towards the water type, soils and precipitation. Its distribution is Orinoco, the left-bank tributaries are clearwater rivers associated principally with high productivity rivers that originate in the poor soils of the high plains, and (whitewater) that provide abundant prey in regions the right-bank tributaries are blackwater streams that marked by highly seasonal rainfall. come from the Guiana Shield (Galvis et al. 2007). The Guyana region of the Orinoco River Basin has The model permitted a more precise calculation of scarcely evolved soils, poor in nutrients and quite potential favorable habitat for the Orinoco crocodile acid (Rosales et al. 2010), that in turn affects the in the Orinoco River Basin. It also identified zones productivity of the rivers there. where environmental conditions (climate, water type)

Figua 7. Crocodylus intermedius.

132 Biota Colombiana 15 - Suplemento 1 - 2014 Biota Colombiana 15 - Suplemento 1 - 2014 133 Potential distribution of the Orinoco crocodile (Crocodylus intermedius Graves 1819) Morales-Betancourt et al. in the Orinoco basin of Colombia and Venezuela

are most suitable for crocodile populations. This Antelo provided limnological data from the Palmarito permits concentration of conservation efforts in areas Foundation. Thanks to German Gálvis for his help to where crocodile populations are most likely to thrive. build the water type map. We also thank María Cecilia Londoño, Liliana Corso, Marcela Portocarrero and The Orinoco Crocodile is endemic to the Orinoco Lina Mesa (IAvH), Antonio Castro (Asociación River Basin, but is only found in a small part of that Chelonia Colombia) and Myriam Lugo for their basin. The very restricted distribution pattern is of assistance in data acquisition. To Donald Taphorn great relevance because it indicates that the areas for the translation of this manuscript. We thank the where current populations remain and those thought IAvH and the Ministerio de Ambiente y Desarrollo to be most favorable to Orinoco crocodiles are crucial Sostenible de Colombia for technical assistance and to the successful conservation of this species. For funding. this reason, it is imperative that the environmental authorities of both countries seriously take into account the areas indicated as most favorable habitat Bibliography when making decisions about territorial planning and development, and avoid ongoing and future negative Antelo, R. 2008. Biología del cocodrilo o caimán del Orinoco (Crocodylus intermedius), en la Estación impacts of agro-industrial, mining, hydropower, and Biológica El Frio, en el Estado de Apure (Venezuela). other projects. Tesis Doctoral. Departamento de Ecología, Universidad Autónoma de Madrid. 336 pp. The high degree of endemism and small number Antelo, R. 2012. Conservación. Pp. 133-147. In: Fundación of existing populations indicate the urgency of Chelonia (Ed.). Historia natural y conservación del implementing in situ conservation strategies already caimán llanero (Crocodylus intermedius Graves, 1819) proposed in the conservation plans and strategies en Colombia. Asociación Chelonia. of both countries, again, and especially in those Castro, A., M. Merchán, M. Garcés, M. Cárdenas & F. drainages where favorable habitat conditions exist Gómez. 2012. New data on the for this species. of the Orinoco crocodile (Crocodylus intermedius) in Colombia. Pp. 65-73. In: Crocodiles. Proceedings of st The model applied predicted which areas are the the 21 Working Meeting of the IUCN-SSC Crocodile Specialist Group. IUCN: Gland, Switzerland. most appropriate as suitable habitat for the Orinoco Crocodile, confirming and reinforcing the hypothesis Clavijo, J. M. & L. F. Anzola. 2013. Elementos claves para la conservación in situ de Crocodylus intermedius that water type and climate variables are strong derivados del seguimiento de metapoblaciones y determinant factors influencing the geographic hábitats en Arauca, Colombia. Revista Colombiana de distribution of this species. The model is a useful Ciencia 5 (2): 560-573. tool for decision makers when planning conservation Domínguez, C. 1998. La gran cuenca del río Orinoco. Pp. of endangered species. However, it should be 39-67. In: Domínguez, C. (Ed.). Colombia Orinoco. remembered that this type of analysis only takes into Fondo FEN, Instituto de Estudios Orinoquenses, account the physical (and in part biological) habitat Bogotá, Colombia. parameters that should be complemented with an Elith, J., C. Graham, R. Anderson, M. Dudı´k, S. Ferrier, A. analysis of the human impacts on the habitat of this Guisan, R. J. Hijmans, F. Huettmann, J. R. Leathwick, A. Lehmann, J. Li, L.G. Lohmann, B. A. Loiselle, G. species (threats and opportunities). A study evaluating Manion, C. Moritz, M. Nakamura, Y. Nakazawa, J. McC. the availability and quality of nesting beaches is also Overton, A. T. Peterson, S. J. Phillips, K. Richardson, needed. R. Scachetti-Pereira, R. E. Schapire, J. Soberón, S. Williams, M. S. Wisz & N. E. Zimmermann. 2006. Novel methods improve prediction of species’ distributions Acknowledgements from occurrence data. Ecography 29: 129-151. Elith, J., S. J. Phillips, T. Hastie, M. Dudík, Y. Chee & C. We thank Andrés Seijas (UNELLEZ-Venezuela) and J. Yates. 2011. A statistical explanation of MaxEnt for Omar Hernández (FUDECI-Venezuela) for sharing ecologists. Diversity and distributions 17: 43–57. their Orinoco Crocodile sighting databases. Rafael

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Mónica A. Morales-Betancourt Potential distribution of the Orinoco crocodile Programa Ciencias Básicas de la Biodiversidad (Crocodylus intermedius Graves 1819) in the Orinoco Instituto de Investigación de Recursos Biológicos basin of Colombia and Venezuela Alexander von Humboldt Bogotá, D. C., Colombia Cítese como: Morales-Betancourt, M. A., C. A. Lasso, L. C. [email protected] Bello y F. de P. Gutiérrez. 2014. Potential distribution of the Orinoco crocodile (Crocodylus intermedius Graves 1819) Carlos A. Lasso in the Orinoco basin of Colombia and Venezuela. Biota Colombiana 15 (Supl. 1): 124-136. Programa Ciencias Básicas de la Biodiversidad Instituto de Investigación de Recursos Biológicos Alexander von Humboldt Bogotá, D. C., Colombia [email protected]

Laura C. Bello Programa Gestión de la Información y el Conocimiento Instituto de Investigación de Recursos Biológicos Alexander von Humboldt Bogotá, D. C., Colombia [email protected]

Francisco de Paula Gutiérrez Universidad de Bogotá Jorge Tadeo Lozano Bogotá, D. C., Colombia Recibido: 4 de julio de 2014 [email protected] Aprobado: 1 de octubre de 2014

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